public class ChengJi {
    public static void main(String []args){
        int score = 90;
        if (score > 80 && score < 100){
            System.out.println("A");

        }else if(score > 70 && score < 80){
            System.out.println("B");

        }else if(score > 60 && score < 70) {
            System.out.println("C");

        }else if(score > 0 && score < 60){
            System.out.println("D");

        }
    }
}
